1. Field of the Invention
The present invention relates to trolleys for gantry cranes and more particularly to a personnel trolley and elevator platform for a cargo container handling gantry crane wherein the gantry is comprised of an outreach boom and inboard girder portions having trolley rails mounted thereon for supporting the cargo container handling trolley.
Large dockside gantry cranes which are used to load and unload standardized cargo containers onto and off of container ships have been employed for many years. Over this period of time they have greatly increased their efficiency of operation through various structural modifications and improvements in operating techniques. Recently, significant investment has been made worldwide by the high volume ports on innovations which are intended to increase the through-put of containers being handled in loading and off-loading container ships. The costs of new dockside container handling cranes have increased significantly due to improvements which increase the container through-put by only a few containers per hour of operation.
In addition to the structural improvements to container handling cranes, their methods of operation have been altered significantly to increase the effectiveness of their operation.
In 1983, OSHA promulgated a new set of regulations applicable to marine terminals (29 CFR Part 1917) which expressly permits longshoring crews to be transported on dockside container crane lifting spreader beams, which are utilized to engage the cargo containers, if certain measures are taken for the safety of the crews. While some crane manufacturers do not concur with OSHA that such movement of personnel is safe, it is a fact that many dockside container crane owners, which have optimized the operation of their container handling equipment, have added personnel platforms and cages to the container handling lifting spreaders, and that longshoring crews are now regularly transported on the spreaders in many container handling terminals.
The crews are transported on the spreaders for two reasons: first, to move the crews from shore to ship and from ship to shore at the beginning and end of the work shifts, and second, to transport longshoremen to the tops of container stacks for the removal or the implacement of container lashings and stacking cones which are employed in the stacking of containers. When it is necessary to move personnel for these purposes, the container crane must cease handling containers in order to move the crews. Concurrently, the lifting spreader acts as the stowage bin for stacking cones, as well as serving as the crew taxi, so the delay includes time for stowing or removing stacking cones in addition to the lost time for movement of the personnel.
Obviously, an improvement in container crane handling efficiency will result if an alternative means can be utilized to move the crews concurrently with container handling rather than consecutively. Equally as obvious is the fact that an independent means for doing so would be desirable but providing such a means on a gantry crane is complicated for many reasons.
2. Description of the Prior Art
A cargo container handling gantry crane of the type to which the present invention can be adapted is disclosed in U.S. Pat. No. 3,945,503 to Cooper, issued Mar. 23, 1976, for a CRANE WITH A VARIABLE CENTER ROPE SUSPENSION SYSTEM. Shown in FIG. 1 thereof is a crane superstructure which supports a gantry comprised of two parts; the inboard trolley-girders and the outboard retractable boom portion. Trolley rails are mounted on the gantry so that a cargo container handling trolley can be mounted on the gantry to move from one end to the other and carry a suspended container thereunder. The design of the crane is such that the load can be moved from one end of the gantry to the other without physically interfering with the crane superstructure. The crane is also mounted on tracks whereby it can be moved along the wharf dockside between ship docking locations. A lifting spreader is suspended under the trolley by a headblock attached to the spreader. The spreader engages the tops of cargo containers for lifting and moving them between dockside and a ship for loading or unloading.
Shown in FIGS. 7 and 8 of the '503 patent is the wire rope reeving arrangement for moving the trolley along the gantry rails and for lifting and lowering the lifting spreader which is suspended from the trolley. The particular hoist reeving arrangement there illustrated, which lifts and lowers the load, is known in the industry as fleet through reeving. Its dominant characteristic is that it allows the hoisting drums and associated hardware to be mounted in a machinery house on the crane superstructure rather than on the gantry or on the trolley. At the same time, the design of the reeving allows free movement of the trolley along the gantry without affecting the overall length of the lifting ropes or the attitude of the lifting spreader and its load when the trolley moves along the rails.
It will be seen that imposing yet another moveable trolley into the reeving of the prior art systems poses considerable problems: especially when the additional trolley would be expected to operate independently of all the lifting spreader wire rope reeving and trolley tow rope reeving and yet concurrently with it when that wire rope reeving is operating and moving cargo containers.